Conventionally, this type of induction heating device is structured, as shown in FIG. 3 that is a vertical sectional view illustrating the induction heating device seen from the front side, a lower part of top plate 203 has heating coil 204 for induction-heating to-be-heated object 202.
Heating coil 204 is divided to inner coil 204a and outer coil 204b. An outer winding of inner coil 204a is electrically connected to an inner winding of outer coil 204b. Inner coil 204a and outer coil 204b are concentrically arranged when seen from the above of main body 201. The center of this concentric pattern corresponds to center 130 of circle 120 of FIG. 1B (which will be described later).
Sensors 205 are each a heat sensitive element such as a thermistor. Sensors 205 are provided at the center of heating coil 204 and at one position between inner coil 204a and outer coil 204b (a position closer to the left side of main body 201 of the induction heating device and a left-side position in FIG. 3). Sensor 205 is pressure-welded to a back face of top plate 203 corresponding to a lower part of to-be-heated object 202 and outputs a signal depending on a sensed temperature. The reason why the configuration as described above is used is that the temperature of to-be-heated object 202 can be generally sensed with a higher sensitivity by placing sensor 205 at a position causing a higher magnetic flux because sensor 205 placed at such a position can improve the uniform heating by the division of heating coil 204 and can prevent to-be-heated object 202 from having an excessively-increased temperature. Temperature calculator 206 senses the temperature of to-be-heated object 202. Temperature calculator 206 calculates the temperature of to-be-heated object 202 based on an output from sensor 205 that is a heat sensitive element. Based on the information obtained from temperature calculator 206, controller 207 controls the power supply to heating coil 204. The conventional induction heating device as described above is disclosed in Japanese Patent Unexamined Publication No. 2003-234168 for example.
In the case of the conventional configuration as described above however, thermal responsiveness and temperature sensing accuracy are deteriorated in a case where to-be-heated object 202 is not placed above sensor 205 when compared with a case where to-be-heated object 202 is placed above sensor 205. This has caused a disadvantage where, when to-be-heated object 202 such as a pan accommodating no food or liquid is heated while to-be-heated object 202 being not placed above sensor 205, the pan may be excessively heated to easily deform for example.